Systems and methods for seismic data acquisition employing clock source selection in seismic nodes

• US 9,207,337 B2
• Filed: 12/12/2007
• Issued: 12/08/2015
• Est. Priority Date: 12/12/2007
• Status: Active Grant

• Current Assignee: WesternGeco LLC
• Original Assignee: WesternGeco LLC
• Inventors: Johansen, Thomas Uteng
• Primary Examiner(s): Murphy, Daniel L
• Application Number:
  US11/954,960
• Publication Number:
  US 20090154289A1
• Time in Patent Office: 2,918 Days
• Field of Search: 181/108, 181/113, 181/122, 326/96, 327/2, 327/7, 327/37, 327/50, 327/60, 327/141, 327/144, 327/147, 327/162, 327/163, 327/291, 327/292, 327/298, 332/112, 367/55, 367/14, 367/21, 367/38, 375/226, 375/239, 375/247, 375/356, 375/373, 375/376, 700/3, 702/14, 702/89
• US Class Current: 1/1
• CPC Class Codes: G01V 1/00 Seismology; Seismic or acoustic prospecting or detecting
• CPC Class Codes: H04L 7/0083 taking measures against momentary loss of synchronisation, e.g. inhibiting the synchronisation, using idle words or using redundant clocks

Abstract

Systems and methods for acquiring seismic data are described, one system comprising one or more seismic sources, a plurality of sensor modules each comprising a seismic sensor configured to sample analog seismic data, each module comprising a comparing unit comprising software; wherein the software in each module tests clock quality by running a sigma-delta modulator from two different clock sources in the node and compares a noise-floor of the modulator when using the different clocks.

Claims

1. A seismic data acquisition system comprising:

one or more seismic sources;

a sensor system for acquiring and/or monitoring analog seismic sensor data, the sensor system comprising a plurality of sensor modules, each module comprising a comparing unit comprising software;

wherein the software in each module tests clock quality by running a sigma-delta modulator from two different clock sources and compares a noise-floor of the modulator when using the different clock sources.

2. The system of claim 1 for performing land seismic data acquisition.

3. The system of claim 1 for performing marine seismic data acquisition.

4. The system of claim 1 wherein the two different clock sources comprise a distributed slave clock, and the module selects its distributed slave clock as the default sensor clock.

5. The system of claim 4 wherein a portion, but not all, of the distributed sensor slave clocks are phase-locked to a master clock by a phase lock loop to improve slave clock quality.

6. The system of claim 5 wherein the master clock is a high precision clock.

7. The system of claim 6 wherein seismic data is upsampled using a linear or nonlinear interpolation technique, based on the amount of drift of each sensor module slave clock relative to the master clock, to increase an effective sampling rate of the seismic data.

8. The system of claim 1 wherein each sensor module comprises a phase lock loop.

9. The system of claim 1 wherein each sensor module comprises a phase lock loop that is engaged only if noise in a distributed sensor slave clock is above a threshold value.

10. The system of claim 9 wherein each sensor module comprises an analog to digital converter (ADC) and a digital signal processor (DSP).

11. The system of claim 1 comprising a base station that is selected from mobile and non-mobile communication devices.

12. The system of claim 1 comprising a data transmission sub-system allowing transmission of data to one or more base stations, which in turn transmit at least some of the data they receive to a recording station.

13. The system of claim 12 comprising a first communication link that transmits seismic data sampled from a seismic sensor to a base station, the base station having a second communication link that receives the seismic data from the sensor modules and transmits the seismic data to the seismic data recording station, the one or more seismic sources having a third communication link that receives commands from the seismic data recording station and transmits seismic source data to the seismic data recording station.

14. A seismic data acquisition system comprising:

one or more seismic sources;

a sensor system for acquiring and/or monitoring analog seismic sensor data, the sensor system comprising a plurality of sensor modules, each module comprising a comparing unit comprising software;

wherein the software in each module tests clock quality by running a sigma-delta modulator from two different clock sources and compares a noise-floor of the modulator when using the different clock sources wherein the two different clock sources comprises a distributed slave clock and a master clock.

15. The system of claim 14 for performing land seismic data acquisition.

16. The system of claim 15 for performing marine seismic data acquisition.

17. The system of claim 16 wherein each sensor module selects its distributed slave clock as the default sensor clock.

18. A method comprising:

a) initiating one or more seismic sources;

b) acquiring reflected analog seismic data using a sensor system, the sensor system comprising a plurality of sensor modules each comprising a comparing unit comprising software;

c) testing clock quality using the software in each module by running a sigma-delta modulator from two different clock sources in each module;

d) comparing a noise floor of the modulator when using the different clock sources; and

e) selecting the clock source from the two different clock sources that provides the best noise floor, or a clock that provides the noise floor below a specified value.

19. The method of claim 18 wherein the two different clock sources comprise a slave clock source, the method further comprising phase-locking the slave clock source if the noise floor when using the slave clock source is over a threshold value, but otherwise not phase-locking the slave clock source in order to conserve power.

20. The method of claim 18, wherein the slave clock source comprises a plurality of slave clock sources, the method further comprising phase-locking a portion, but not all, of the sensor slave clock sources to a master clock to improve slave clock source quality.